Our objective is to investigate physiologic control mechanisms of finger blood flow in normal subjects and in patients with idiopathic Raynaud's disease, Raynaud's phenomenon secondary to scleroderma, hypertension, and coronary artery vasospasm. Digital arteriolar critical closing presure will be used to quantitatively measure response in vascular tone. Total fingertip blood flow will be measured by air or water displacement venous occlusion plethysmography. Capillary blood flow will be determined by the disappearance rate of a local depot injection of radioisotope in the fingertip. Fingertip arteriovenous shunt flow will be calculated by subtracting capillary from the total flow. Intra-arterial infusions of isoproterenol and dopamine will be used to establish possible beta adrenergic or dopaminergic vasodilator mechanisms, and dose response sensitivity will be compared between normals and patients with Raynaud's disease. Quantitative measurements of changes in vascular tone to local and environmental cooling will be made to compare vasoconstrictor responses in normals and patients with Raynaud's diseases. In patients with hypertension, digital vascular tone and cold vasoconstrictor responses will be measured before and during treatment with an angiotensin converting enzyme inhibitor (Captopril SQ14225). Differences in vasoconstrictior responses to cold will also be sought in patients with coronary artery vasospasm.